Various mechanical bindings for snowboards are known. Typically these comprise a cage of straps that is secured directly to the snowboard that the user straps his foot into. The user's foot is effectively bound to the snowboard. Other systems are known in which a mechanical quick release fitting is provided on the bottom of the user's boot and this connects with a corresponding fitting secured to the board. Such connection systems are also referred to as “bindings”. The known bindings have a fixed angular position with respect to the board during use. They can be loosened to adjust the position of the binding using a screwdriver or allen key. This system is used to adjust the binding set-up to the rider's preference before riding takes place. However, bindings are also known in which rotation is enabled while the boot is fitted in order to allow the rider to more easily use a lift, or to move easily when there is no slope.
JP2003/024496 discloses bindings that are attached to a snowboard via setting device that comprises a base member attached to screw holes in the board; a rotating member rotatably supported against the base member; a pressure contact plate pressed into contact with part of the rotating member; and a fixing means for fixing the pressure contact plate in place using fixing screws. By loosening the fixing screws, which can be wing nuts, the rider can release the pressure contact plate, thereby allowing the binding to rotate.
U.S. Pat. No. 6,450,511 discloses a swivelable mount for the boot bindings of a snowboard or wakeboard or the like, including a low profile top plate which joins to the binding structure and a circular bottom plate which attaches to a snowboard. The two plates are slideable relative to each other when a spring pin, mounted to the top plate and extending through a hole in the bottom plate, is drawn upwardly, corresponding to an unlocked, rotatable condition of the top plate for use when on a lift, or manoeuvring the snowboard on flat ground. During riding, the spring-loaded pin is released and engages the opposing bottom plate hole to prevent the top plate from rotating and keep the snowboard rider firmly attached to the snowboard.
U.S. Pat. No. 6,302,428 discloses a snowboard step-in binding having a rotatable sole holder that can be moved between two limit positions and can be opened using an opening lever.
It is a common preconception that bindings should hold the rider's foot in a fixed position whilst the rider is snowboarding down a slope or performing tricks. As a result many of the known bindings are designed not to allow the boot to rotate in the plane of the board or perpendicular to the board during such use.
However, it has been recognised that it may be useful to allow the feet to rotate under some circumstances during use.
In U.S. Pat. No. 6,022,040 several problems with permanently fixed binding systems are discussed. These include the problems of propelling the board along on the flat, which is known as “skating”, and using ski lifts easily without needing to place the feet at an unnatural angle. These problems are solved to some extent by the above described “quick-release” systems, which allow the rider to switch to a rotating binding mode when not actually boarding. U.S. Pat No. 6,022,040 also discusses the problem of strain on the knees resulting from adopting an unnatural angle of the feet, and further identifies the problem of changing riding style whilst boarding, and the need for freedom of movement during aerial manoeuvres. To solve all these problems, this document discloses a system in which the feet are allowed to rotate freely about a limited arc when turning is not taking place, but in which during turning radial ridges engage with the base of the riders boot, and prevent rotation. Engagement of the ridges during turning occurs due to the shift of the rider's body weight.
This system has the disadvantage that a catch structure must be attached to the base of the boot, which could hinder the rider's movement when not on the board, and also could prevent the rider from using the boot with other binding systems. Rotation through much more than 90° is not allowed, which could be limiting in some situations. Additionally, by preventing rotation when the rider's body weight shifts during turning, this system would also fix the feet in place in the event of a fall in which similar shifts in weight occurred. The feet and knees could therefore become stuck at a bad angle during a fall, and an injury could result.
As discussed in U.S. Pat. No. 6,022,040, the design of snowboard bindings can contribute to injuries sustained by snowboarders. The incidence and causes of such injuries is discussed in more detail in “Snowboarding Injuries” by Craig C. Young, M.D. and Mark W Niedfeldt, M.D. of the Medical College of Wisconsin, published in American Family Physician, Vol. 59/No. 1, Jan. 1, 1999. In that paper, knee injuries and ankle injuries were found to account for around 16% and 17% of snowboarding injuries respectively. Therefore, if a binding places less strain on the knees and ankles, then the risk of injury should be reduced.
Many snowboarding injuries take place when the rider falls. Beginners often fall regularly and therefore a high percentage of injuries occur during the rider's first experience of snowboarding or in their first season of snowboarding. More advanced riders may fall when attempting jumps or other aerial manoeuvres. One mechanism of ankle injury is a forcing of the ankle into dorsiflexion and inversion, which may occur during a landing from an aerial manoeuvre or a jump, especially when the landing has been over-rotated. Thus, a binding that cannot rotate in a fall due to weight shift of the rider, as might be the case with U.S. Pat. No. 6,022,040, would not prevent these types of injuries.
JP 2000-070432 discloses a system for joining a binding to a board which uses a top plate that is connected to a bottom plate via a bearing in-between them to allow rotational movement of the binding with respect to the board.
By allowing full rotation at all times, the feet and knees can always be placed as the rider wants them, and rotation can always occur during a fall in order to avoid the risk of injury, in particular knee injury caused by restricted foot movement. Additionally by allowing more freedom of movement the board can be easier to use, and there is greater flexibility in the positions that can be taken up during use.
On certain sections of a slope, for example, the rider may prefer to have his foot more in line with the direction of travel, e.g. for speed, or more perpendicular e.g. for turning. It will also relieve some of the strain on the ankle whilst on a chair lift if the front foot can be twisted into a different position with respect to the board. Free rotation may also give rise to new styles of riding a board and allow the more expert user to perform more complex manoeuvres.
However, bearings are by their nature precision components, and therefore can be complex to repair and maintain. It is likely that in a snowboarding environment snow and dirt would penetrate into the casing of a bearing and it would not be easy to clean such a system. In other boarding applications, dust, sand, water or mud could get into the casing. As a result, a bearing based system may be liable to failure due to wear and jamming from trapped dirt, and would be at risk of corrosion of the metal parts if moisture is retained in the casing after use.
Additionally, metal components may suffer when exposed to extremes of cold, as metals generally have high thermal expansion coefficients, which means that additional stresses would be present in a metal device due to differential contraction of differing metals or different shapes in the cold. This could lead to inefficient operation, jamming, or fatigue failure as a result of contraction and expansion when moving the board from a warm building to the cold snow outside. The metal also has to be chosen carefully to avoid a situation where it is below its brittle/ductile transition temperature in normal use under the sub-zero temperatures experienced on the ski slopes.